<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .red {
            color: red;
        }

        .green {
            color: green;
        }

        .blue {
            color: blue;
        }
    </style>
</head>
<body>
<div class="red">
    <p>red</p>
</div>
<div class="green">
    <p>green</p>
</div>
<div class="blue">
    <p>blue</p>
</div>
<script>
/*
    普通的方法
 */
</script>
</body>
</html>